Researchers have been unable to clearly examine the specific psychological mechanisms through which social support buffers stress effects on cardiovascular reactivity, and the boundary conditions under which social support operates. The present study, based on the stress-buffering model of social support, will examine patterns of cardiovascular reactivity and recovery, via impedance cardiography, across different stressors, as well as positive affective states as psychological mediators. Pet owners' bonds with their pets will be used as a positive supportive condition to compare with human support because the positive emotions evoked in the presence of one's pet may be identical to the positive emotions felt with a supportive other in non-evaluative stressors. Aim #1 will replicate past findings, comparing friend-support and no support in two different stressful situations, in order to examine potential psychological mediators linking social support to cardiovascular reactivity and recovery. Aim #2 and #3 will extend Aim #1 by comparing pet support with no support, and then, comparing pet support with friend support. Discovery of such mediation pathways has important implications for the study of social support effects on cardiovascular health. [unreadable] [unreadable]